1. Field of the Invention
The present invention relates in general to an EMI (electromagnetic Interference) shielding film and a front filter including the same in a flat panel display device, more particularly, to an EMI shielding film and a front filter including the same in a flat panel display device, wherein a manufacturing process for the EMI shielding layer is much simplified and thus, its cost of manufacture is considerably lowered.
2. Discussion of the Background Art
Thanks to the technological developments in recent years, flat panel displays have come into wide use. Typical examples of flat panel displays are LCDs (liquid crystal displays) and plasma display panels.
Particularly, plasma display panels (hereinafter referred to as PDPs) display images including characters or graphics by irradiating phosphors out of 147 nm-ultraviolet rays that are generated by a discharge of different compositions of inert gas mixtures, such as, He+Xe, Ne+Xe or He+Ne+Xe.
The PDP technology is now at mass production stage, and recent advances in PDP technologies made easier to manufacture slim PDPs and to provide highly improved picture quality. Especially, in case of a three-electrode alternating current (AC) surface-discharge PDP, charge particles formed by a discharge (i.e. wall charges) are stacked on the surface, which in turn protect electrodes from sputtering originated by the discharge. Therefore, the three-electrode AC surface discharge PDP consumes less voltage and has a long lifespan.
FIG. 1 is a perspective view of a discharge cell structure of a related art PDP.
Referring to FIG. 1, a discharge cell of the three-electrode AC surface-discharge PDP includes a scan electrode (Y) and a sustain electrode (Z) formed on an upper substrate 10, and an address electrode (X) formed on a lower substrate 18. The scan electrode (Y) and the sustain electrode (Z) respectively includes transparent electrodes (12Y and 12Z), and bus electrodes (13Y and 13Z) formed on an edge of the transparent electrodes (12Y and 12Z) and having a smaller line width than that of the transparent electrodes (12Y and 12Z).
In general, the transparent electrodes (12Y and 12Z) are made from Indium-Tin-Oxide (ITO) and formed on the upper substrate 10. The bus electrodes (13Y and 13Z) are typically made of metals like chrome (Cr) and formed on the transparent electrodes (12Y and 12Z). The major function of the bus electrodes (13Y and 13Z) is reducing voltage drop caused by the highly resistive transparent electrodes (12Y and 12Z). Also, an upper dielectric layer 14 and a protective film 16 are layered on the upper substrate 10 on which the scan electrode (Y) and the sustain electrode (Z) are formed side by side. The charge particles generated by a plasma discharge (i.e. wall charges) are stacked on the upper dielectric layer 14. The protective film 16 protects the upper dielectric layer 14 from damages caused by a sputtering during the plasma discharge, and improves the emission efficiency of secondary electrons. The protective film 16 is usually made from magnesium oxide (MgO).
A lower dielectric layer 22 and a barrier rib 24 are formed on the lower substrate 18 provided with the address electrode (X). The surface of the lower dielectric layer 22 and the barrier rib 24 are coated with fluorescent layers 26. The address electrode (X) is formed at right angles to the scan electrode (Y) and the sustain electrode (Z). The barrier rib 24 is formed in a strip or lattice pattern, and prevents ultraviolet rays and visible rays generated by a discharge from being leaked to the adjacent discharge cells.
The fluorescent layers 26 are excited by ultraviolet rays generated during the plasma discharge to generate one of visible rays in red, blue, or blue. A mixed inert gas is injected into a discharge space defined between the upper and lower substrates 10 and 18 and the barrier rib 24.
In the PDP with the above-described discharge cell structure, a front filter 30 is installed at the upper substrate 10, as shown in FIG. 2, in order to shield electromagnetic wave and to prevent reflection of external light.
There are two types of front filters 30: glass type front filters and film type front filters. Both glass type front filters and film type front filters are provided with an EMI shielding film 34, as shown in FIG. 3, to shield electromagnetic waves generated from the PDP.
The EMI shielding film 34 includes a mesh unit 38 provided with conductive meshes 36, a mesh frame 32 for surrounding the outside of the mesh unit 38, and a black frame 40 superposed upon the mesh unit 38 and the mesh frame 32.
The mesh unit 38 is formed of conductive meshes 36 being intersected with each other. To create the conductive meshes 36, a mesh metal layer of silver (Ag) or copper (Cu) undergoes a photolithography process. These intersected conductive meshes 36 provide square shaped holes tilted at a bias angle (θ) to transmit visible light rays therethrough.
The mesh frame 32 surrounds the outside of the mesh unit 38 to support the mesh unit 38. Also, the mesh frame 32 and a case (not shown) electrically connected to the mesh frame 32 are earthed to a ground voltage, and absorb electromagnetic waves emitted from the PDP and discharge them. In this manner, the electromagnetic waves are not emitted to outside. The mesh frame 32 is usually made from silver (Ag)) or copper (Cu).
The black frame 40 defines an effective display area to make outlines of the screen visibly distinctive. The black frame 40 is relatively broader than the mesh frame 30, and made from black ceramic materials.
A related art black frame for the glass type front filter was formed by depositing a black ceramic material on the surface of a glass substrate (not shown) and then performing a patterning process thereon. However, because the related art method required an additional process for forming the black frame, the overall process got more complicated.